When performing a brachytherapy procedure, a physician or technician often must design and assemble the load pattern of radioactive brachytherapy seeds to be implanted into the body. With reference to FIG. 1, a perineal template 1 is supported on a patient stabilizing fixture 2 adjacent to a patient 3 in a manner to minimize any relative displacement between the template 1 and the patient 3. The template 1 includes an array of through-passages, where the passages arranged in a known grid pattern. The physician, knowing the location and size of the target tissue to be treated, will design the dose plan, ie, the three-dimensional array of brachytherapy seeds which will be implanted within and about the target tissue.
During implantation of seeds, perineal template 1 is utilized to direct the implant needles 4 into the prostate according to the dose plan. The template 1 utilizes a standard X-Y coordinate system. The template 1 also provides accurate guidance of the implant needle 4 through the template 1, providing penetration into the patient perpendicular to the template. The standard seed utilizes an 18 gauge implant needle, which requires a template for this specific sized needle. Although the X-Y coordinate system is common among different manufacturers of templates (labelling may be slightly different) the mechanism for attachment to the stabilizing table can vary greatly. There are currently dozens of different perineal templates on the market, each tailored to different attachment mechanisms (or “leg designs”).
Thus, there are numerous perineal template designs on the market, each employing a particular design for its array of through passages and accommodating a particular leg design. For example, the template designs may consist of a standard X-Y hole pattern, an alpha numeric identification system for the X-Y coordinates (unique to the dose planning system used), or a unique profile at the bottom of the template to accommodate different ultrasound probe designs. The leg designs can vary to accommodate the different stepper stabilizer models, which can dictate different distances between the legs, and different leg diameters, or incorporate adjustable collars on the legs to allow for positioning of the grid based upon different stepper stabilizers. There are also a number of different adaptors that allow for connecting one style of template to a specific style of stepper stabilizers.
Finally, there are numerous dose planning software packages specific to available implant templates. These software packages will provide specific dose profiles by directing that a needle with a particular brachytherapy load be inserted into an identified through-passageway. As different templates employ different schemes for labeling the rows and columns of their through-passageways, the dose planning software takes this into account when presenting the dose plan.
A new smaller diameter seed has been designed that utilizes a smaller diameter 20-gauge needle to implant the seeds. A perineal template that has smaller diameter passageways is required for accurate placement of needles and seeds. Initial implants were supported by replicating the template being used at a specific clinic with a 20 gauge version, at a great expense.
With the market opening on the smaller diameter seed (and thus smaller needle) a more cost efficient method of supporting the surgical implant is needed.
A 20-gauge template is required as the thinner diameter of the 20-gauge needles results in a standard 18-gauge template having through-passages which are too large in diameter for ensuring proper placement of a 20-gauge needle. That is, the longitudinal axis of the 20-gauge needle will be positioned off-axis of the longitudinal axis of the 18-gauge needle passageway of the template. An off-axis needle will result in, brachytherapy seeds being delivered in deviation of the dose plan.
It has thus far been very difficult, and not cost effective, to establish the correct style needed for each new user site that wants to switch to smaller diameter seeds (and thus needles). In some cases the only option would be to create a unique perineal template to accommodate a particular site. This has been done at a cost well in excess of $1000 per template. Often, several templates are needed per user site, further complicating and increasing the expense of providing a new line of perineal templates for the new smaller-diameter seeds.
Therefore, given the ubiquity of templates sized for accommodating 18-gauge needles, and the cost involved in providing a templates for 20-gauge needles for all of the available leg designs, there is a need in the art for a simple device for ensuring the proper centering of a brachytherapy needle within the through-passages of the existing templates.